Subsampled terahertz data reconstruction based on spatio-temporal dictionary learning

In this paper, the problem of terahertz pulsed imaging and reconstruction is addressed. It is assumed that an incomplete (subsampled) three dimensional THz data set has been acquired and the aim is to recover all missing samples. A sparsity-inducing approach is proposed for this purpose. First, a simple interpolation is applied to incomplete noisy data. Then, we propose a spatio-temporal dictionary learning method to obtain an appropriate sparse representation of data based on a joint sparse recovery algorithm. Then, using the sparse coefficients and the learned dictionary, the 3D data is effectively denoised by minimizing a simple cost function. We consider two types of terahertz data to evaluate the performance of the proposed approach: THz data acquired for a model sample with clear layered structures (e.g., a T-shape plastic sheet buried in a polythene pellet), and pharmaceutical tablet data (with low spatial resolution). The achieved signal-to-noise-ratio for reconstruction of T-shape data, from only 5% observation was 19 dB. Moreover, the accuracies of obtained thickness and depth measurements for pharmaceutical tablet data after reconstruction from 10% observation were 98.8%, and 99.9%, respectively. These results, along with chemical mapping analysis, presented at the end of this paper, confirm the accuracy of the proposed method.     

Dynamic modeling and redundant force optimization of a 2-DOF parallel kinematic machine with kinematic redundancy

High precision is still one of the challenges when parallel kinematic machines are applied to advanced equipment. In this paper, a novel planar 2-DOF parallel kinematic machine with kinematic redundancy is proposed and a method for redundant force optimization is presented to improve the precision of the machine. The inverse kinematics is derived, and the dynamic model is modeled with the Newton–Euler method. The deformations of the kinematic chains are calculated and their relationship with kinematic error of the machine is established. Then the size and direction of the redundant force acting on the platform are optimized to minimize the position error of the machine. The dynamic performance of the kinematically redundant machine is simulated and compared with its two corresponding counterparts, one is redundantly actuated and the other is non-redundant. The proposed kinematically redundant machine possesses the highest position precision during the motion process and is applied to develop a precision planar mobile platform as an application example. The method is general and suitable for the dynamic modeling and redundant force optimization of other redundant parallel kinematic machines.     

Li-function activated ZNN with finite-time convergence applied to redundant-manipulator kinematic control via time-varying Jacobian matrix pseudoinversion

This paper presents and investigates the application of Zhang neural network (ZNN) activated by Li function to kinematic control of redundant robot manipulators via time-varying Jacobian matrix pseudoinversion. That is, by using Li activation function and by computing the time-varying pseudoinverse of the Jacobian matrix (of the robot manipulator), the resultant ZNN model is applied to redundant-manipulator kinematic control. Note that there are nine novelties and differences of ZNN from the conventional gradient neural network in the research methodology. More importantly, such a Li-function activated ZNN (LFAZNN) model has the property of finite-time convergence (showing its feasibility to redundant-manipulator kinematic control). Simulation results based on a four-link planar robot manipulator and a PA10 robot manipulator further demonstrate the effectiveness of the presented LFAZNN model, as well as show the LFAZNN application prospect.     

工业无线技术在大型石油化工罐区自动化的应用

随着无线技术的迅速发展，在工业自动化领域的应用越来越广泛。本文介绍工业无线技术标准ISA100．11a及无线解决方案，霍尼韦尔基于ISA100．11a工业无线标准的解决方案在大型石油化工罐区自动化的应用。     

化工企业员工退出机制探讨

从理顺人力资源劳动关系角度,探讨化工企业如何在法律法规的基础上,建立灵活规范的员工柔性退出机制,运用经济手段、协商方式,让有志于自我发展的富余员工走向市场,化工企业的用工制度走出一条切实可行的道路。     

电液伺服加载力差信号前馈控制

提出利用电液加载前馈舵机系统力差信号减少多余力的控制方法。传统的方法是测量舵机近似的速度信号进行前馈控制,力差前馈控制是测量舵机系统产生加速度的力信号进行前馈控制。仿真结果表明,采用该方法消除多余力的效果很好。     

A fractional approach for the motion planning of redundant and hyper-redundant manipulators

The trajectory planning of redundant robots through the pseudoinverse control leads to undesirable drift in the joint space. This paper presents a new technique to solve the inverse kinematics problem of redundant manipulators, which uses a fractional differential of order α to control the joint positions. Two performance measures are defined to examine the strength and weakness of the proposed method. The positional error index measures the precision of the manipulator's end-effector at the target position. The repeatability performance index is adopted to evaluate if the joint positions are repetitive when the manipulator execute repetitive trajectories in the operational workspace. Redundant and hyper-redundant planar manipulators reveal that it is possible to choose in a large range of possible values of α in order to get repetitive trajectories in the joint space.     

海洋石油生产储油轮发电机组控制技术研究

海洋石油生产储油轮作为海洋油气开发系统的核心部分,其发电机组控制技术要求可靠性高、抗干扰能力强、实时性好。基于西门子S7～300／400PLC,提出采用层次化冗余控制结构构建发电机组控制系统：底层控制结构划分为各独立子系统,中间层控制站控制底层子系统协调工作,顶层系统实现人机交互以及系统监控;设计了各层控制系统硬件及软件结构;论述了层之间数据通信实现方式。系统具有开放性、智能性及易维护性等优点。     

液压驱动冗余振动台自由度控制及内力协调

振动台是一种对高层建筑、大型桥梁和基础设施等大型结构进行抗震性能试验的重要设备。为了提高振动台有效载荷,以便进行大尺寸或全尺寸结构试验,振动台通常采用液压驱动冗余并联机构。本文首先根据液压驱动冗余振动台机液作用机理,建立了冗余振动台的整体机液动力学模型,并提出一种适用于液压驱动冗余振动台的自由度控制结构。之后,针对冗余驱动内力耦合问题,采用基于雅克比矩阵伪逆的内力协调控制方法,协调控制各激振器间的出力,减少各个激振器间的内力耦合。最后,通过仿真分析,验证了本文提出的自由度控制和内力协调控制的有效性。     

基于罗克韦尔ControlLogix的玻壳成型冗余自控系统设计

本文介绍了基于美国罗克韦尔公司ControlLogix控制器的玻壳成型冗余自控系统,应用基于PROFIBUS—DP、MPI及Ethemet的网络通信手段,通过软冗余的方式实现对生产线设备的控制。作者阐述了该冗余控制系统的基本工作原理、软硬件构成与通信网络配置、功能特点及程序设计等方面的内容。